Glossary

FACIESIn geology, the composition and characteristics of a rock formation.

FARM INWhen a company acquires an interest in a block by taking over all or part of the financial commitment for drilling an exploration well.

FARMOUT An arrangement under which a portion of an interest in petroleum and natural gas rights is assigned in consideration for the assignee agreeing to explore or drill (and perhaps equip) one well or several wells at his sole expense; subsequent development and equipment cost, if any, and income and operating expenses are shaped by participants on an agreed basis.

FAULT/FAULT BLOCKA discontinuity in a rock formation caused by fracturing of the earth's crust. In oilfield terms a Fault Block is a compartment of a rock formation surrounded or partly surrounded by faults, which may have sealed in hydrocarbons separately from the rest of the formation.

FIELDAn area consisting of a single reservoir or multiple reservoirs all grouped on, or related to, the same individual geological structural feature or stratigraphic condition. The field name refers to the surface area, although it may refer to both the surface and the underground productive formations.

FILTER CAKE/FILTRATEBuild up of mud solids or filtrate on the wall of a well. This helps seal and stabilize the rock face, but too much can cause sticking of the drill string. See also Differential Pressure.

FISH/FISHINGAny unwanted object down a well, commonly the lower end of a drill string which has broken off. "Fishing" is trying to recover the Fish, using various attachments to the drill stem or wireline, known as fishing tools.

FLOWING PRESSURE Pressure registered at the wellhead of a flowing well.

FOOTAGE/FOOTAGE RATEPenetration rate in drilling. Footage Rate may also be a form of remuneration under a drilling contract. Often referred to as ROP (Rate of Penetration).

FORMATIONA rock deposit or structure of homogeneous origin and appearance.

FORMATION DAMAGEDamage to the reservoir rock around a well due to e.g. plugging with mud, or infiltration by water from the well.

FRACTURINGThe process of cracking open the rock formation around a well bore to increase productivity. This is normally done by applying hydraulic pressure down the well bore.

FREEHOLD LEASEAn agreement with an individual which provides for the petroleum and natural gas rights underlying a given area.

FREEHOLD ROYALTYA royalty based on production paid to the owner (anyone other than the crown) of the producing lease.

GAS CAPFree gas, separate from, but overlying an oil zone that occurs within the same producing formation as oil. Since gas is lighter, it occupies the upper part of the reservoir.

GAS KICKIncrease of down hole pressure above that exerted by the column of drilling fluid in a well, allowing gas to escape to the surface. If not controlled this could develop into a blowout.

GAS/OIL RATIO (GOR)The proportional amount of gas to oil liquid occurring in production from a reservoir, usually expressed as cubic feet per barrel.

HORIZON Distinct layer or group of layers of rock.

HYDROCARBONS Organic chemical compounds of hydrogen and carbon whose densities, boiling points, and freezing points increase as their molecular weights increase. The molecular structure of the most common petroleum hydrocarbon compounds varies from the simplest - methane, a constituent of natural gas - to the very heavy and complex.

IMPERMEABLE ROCKA rock with restricted or poorly-communicating pore spaces, such that hydrocarbons will not flow through it.

INFILL DRILLING Drilling of wells according to a planned pattern and spacing to achieve full production from a new field.

IN PLACEDescription of the total hydrocarbon content of a reservoir, as distinct from 'Reserves' which can be 'recovered' or produced. Oil or gas in place (OIP, GIP) before the start of production is known as Oil or Gas Originally in Place or Initially in Place. (e.g. STOOIP = Stock Tank Oil Originally in Place; GIIP = Gas Initially in Place).